1. Field of the Invention
The present invention relates to technology for controlling the temperature of a substrate to a desired temperature in a heat exchange plate, which either heats or cools a substrate, like a semiconductor wafer heating/cooling plate in a semiconductor manufacturing apparatus.
2. Description of the Related Art
For example, in order to heat or cool a semiconductor wafer in a semiconductor manufacturing apparatus, there is generally employed a system, wherein separate heat exchange plates are provided for heating and cooling, and a wafer is transported therebetween by a robot. Each heat exchange plate used in this type of system has a large heat capacity with little temperature fluctuation, and static temperature control is performed such that the temperature of each plate is maintained constant.
Conversely, there is also a system, which furnishes both heating and cooling functions in a single heat exchange plate. In such system, it is required to use a high response plate with a small heat capacity, and to dynamically control the operation thereof from a low temperature state to a high temperature state, and vice versa. A heat exchange plate is generally a circular flat-shaped receptacle having a cavity, within which a heating medium flows. A wafer is placed on the upper surface thereof, and the temperature of the wafer is controlled by the heating medium fluid flowing inside the heat exchange plate. Further, there is also a system, wherein foil heaters (heat wire heaters wired in a foil-shaped pattern) for heating a wafer are applied on the top and bottom surfaces of a heat exchange plate.
In the latter system, high-speed, high precision temperature control performance is required to enhance product yield while achieving high throughput. To completely satisfy this requirement, improvements will most likely be needed in a variety of aspects, such as control method, and plate structure, and one important aspect thereof is to keep the temperature distribution on the surface of the wafer extremely small.
However, for the above-mentioned heat exchange plate, since, on the plate surface, an approximately central zone, on which a wafer is placed, and a peripheral zone thereto differ in the heat capacity and in the heat transfer characteristic, there occur temperature distribution irregularities in a concentric ring shape in the wafer as well. Further, an inlet/outlet of the above-mentioned heating medium fluid is provided in this plate, and the zone related thereto has a heat capacity and heat transfer characteristics different from those of the above 2 zones. This is also another reason to cause wafer temperature distribution irregularities.
A heat exchange plate of an International Publication No. WO98/05060 that is supposed to solve for these problems is constituted such that the plate surface is divided into the above-mentioned 3 zones which have different heat capacities and different heat transfer characteristics from one another, that is, an approximately central zone, a peripheral zone thereto, and a fluid inlet/outlet zone, and independent electric circuit foil heaters are attached thereto, respectively, so that temperature control is performed independently.
However, there are a number of problems with this heat exchange plate, too. The first is that the leads of the foil heaters come beneath a placed wafer. A lead portion, unlike a heat generating portion of a foil heater, has temperature differences in itself, which causes temperature distribution to also occur in a wafer. The second is that a fluid inlet and outlet differ greatly in the heat transfer characteristic. The third problem arises from the fact that a temperature sensor is disposed in each zone, and temperature is controlled in each zone. For example, when a certain zone is away from a wafer, even if the temperature of that zone is controlled to the same temperature as the other zones, it is not possible to guarantee that wafer temperature distribution will be uniform. There are cases in which a wafer does not achieve a target temperature, unless the temperature in the vicinity of the above-mentioned fluid inlet/outlet in particular is made either a higher temperature or a lower temperature than the wafer target temperature.
Consequently, an object of the present invention is to solve the above-mentioned problems, and to make uniform the temperature distribution of a substrate that is undergoing heat treatment on top of a heat exchange plate.
A substrate temperature control plate according to the present invention comprises a plurality of zones obtained by partitioning this substrate temperature control plate, temperature sensors, which are directly under a substrate, and are respectively disposed in locations that receive the respective affects of the plurality of zones so as to detect the temperatures of the locations thereof, and heaters, which perform temperature control independently for the respective plurality of zones.
Each of the temperature sensors detects the temperature of the location beneath a substrate where the sensor itself is disposed, and the heaters independently control the respective plurality of zones in accordance with each detected temperature. According to this constitution, the detected temperatures of a plurality of temperature sensors reflect the temperatures of corresponding locations of a substrate. Therefore, by controlling on the basis of these detected temperatures the zonal heaters that have an affect on these temperatures, it is possible to evenly control the temperatures of a plurality of locations of a substrate, that is, to favorably and uniformly control the temperature of an entire substrate.
In a preferred aspect of the embodiment, the constitution is made such a plurality of zones are segmented into portions which differ either in the heat capacity or in the heat transfer characteristic.
For example, when a substrate temperature control plate related to this aspect of the embodiment has a cavity on the inside through which passes a heating medium fluid for controlling the temperature of a substrate, and comprises an inlet for supplying a heating medium fluid to the cavity, and an outlet for discharging a heating medium fluid from the cavity, the abovementioned plurality of zones are a first zone, which is in a location, which surrounds a substrate on the outside of the outer circumference of a substrate, a second zone which is located directly beneath a substrate, a third zone of the vicinity of the outlet, and a fourth zone of the vicinity of the inlet. Since these four zones are portions which are largely different from one another in the heat capacity or in the heat transfer characteristic, it is very effective to segment into and independently control the temperature of these zones from the standpoint of making the temperature of an entire substrate uniform.
In a preferred aspect of the embodiment, heaters are bonded to the top surface and bottom surface of a substrate temperature control plate so as to be mutually symmetrical, so that this substrate temperature control plate becomes substantially vertically symmetrical over its entirety. For example, when a substrate temperature control plate comprises a first, second, third, and fourth zones as described hereinabove, a substrate temperature control plate related to this aspect of the embodiment has a first, second, third, and fourth heater corresponding to the above-mentioned first, second, third, and fourth zones, respectively, and these heaters are bonded to the top surface and bottom surface of the substrate temperature control plate so as to be vertically symmetrical. With a constitution such as this, a temperature difference between the top surface and the bottom surface of a plate can be substantially eliminated, and thermal deformation of a plate occurring in accordance with this temperature difference can be suppressed.
In a preferred aspect of the embodiment, first, second, third, and fourth temperature sensors are disposed in said second zone, the first temperature sensor is disposed in a location of the second zone that is close to the first zone, the second temperature sensor is disposed in a location approximately central location of the second zone, the third temperature sensor is disposed in a location of the second zone that is close to the third zone, and the fourth temperature sensor is disposed in a location of the second zone that is close the fourth zone.
In a preferred aspect of the embodiment, irregularities of temperature distribution in an entire plate caused by leads of a heater of a certain zone are compensated for by a heater of another zone. Thereby, the temperature of an entire substrate can be made more favorable and uniform.
A substrate temperature control plate according to the present invention is provided, for example, in a substrate temperature control apparatus as follows. This substrate temperature control apparatus comprises said substrate temperature control plate, a temperature determining device, and temperature controlling means. The temperature determining device determines a respective target temperature of each of said plurality of zones based on a temperature detected by said temperature sensor. The temperature controlling means performs temperature control such that a respective target temperature that the temperature determining device has determined is established in each of the plurality of zones.